Plane GeometryUnit 7 - Quadrilaterals

Section 1.6 – Classify PolygonsDay 1

WARM-UP

Grab a worksheet from the front table and complete it.

What can we classify the object that the individual is standing on?

PLANE

What exactly is a plane?

PLANE – 2 dimensional object that extends

infinitely in two directions.

What happens if I cut a shape out of a plane?

We have now created a polygon.

Okay, so what is a polygon?

Polygon – closed plane figure with the following two properties:1)It is formed by three or more line segments, a.k.a. the sides.2)Each side intersects exactly two sides, one at each endpoint, so that no two sides with a common endpoint are collinear.

What are the parts of a polygon? How do I label it?

Sides and Vertices (plural of vertex) are the parts.List the vertices in consecutive order.

Vertex

Side

D C

B

A

ELabel:

Pentagon ABCDE or Pentagon CBAED

Convex vs Concave?

Convex – no line that contains a side of the polygon contains a point in the interior of the polygon.Concave – line contains a point in the interior.Convex

ConcavePoint in

the interior

InteriorInterior

How do we classify?

Number of Sides

Types of Polygon

Number of Sides

Types of Polygon

3 Triangle 8 Octagon

4 Quadrilateral 9 Nonagon

5 Pentagon 10 Decagon

6 Hexagon 12 Dodecagon

7 Heptagon n N-gon

3

By the number of sides:

Are there special types of polygons?

Yes, but only for convex polygons:Equilateral – all the sides are congruentEquiangular – all the angles are congruentRegular – convex polygon that is both equilateral and equiangular

1.6 Answers

1. No, curved edges2. Yes, Concave3. Yes, Convex4. Pentagon, Regular5. Quadrilateral,

Equilateral6. Triangle7. Hexagon

8. 8x – 6 = 4x + 224x = 28x = 750 feet

9. 3x + 63 = 7x – 45-4x = -108x = 27144o

1.6 Answers

10. -2x + 41 = 7x - 40-9x = -81x = 923 km

15. Images Vary16. Images Vary17. Images Vary18. Images Vary

19. 2x = x + 30x = 30

20. 3x + 32 = 13x + 2710x = 5x = ½

21. x2 – 12 = 2x2 – 61 x2 = 49x = 7